The complex interaction between Alzheimer drivers and aging Project Summary/Abstract (30 lines of text) The greatest risk for Alzheimer?s disease is age. This extremely tight correlation with age has no explanation. However, most of what know about Alzheimer?s comes from early onset cases. We will utilize the 100 cases of early onset AD stored in the Colombian brain bank all with the same PSEN1[E280A] mutation to determine the full range of pathology observed due to a monogenic defect and compare these data to sporadic older onset disease. Some of the Colombian individuals in the bank have had amyloid and tau PET studies. In sporadic disease among the elderly, brain changes related to aging are frequent and in the absence of their clear delineation, treatments targeted solely at dominant genetic forms of the disease may be ineffective. Factors which might distinguish and promote AD in the elderly include inflammation, compromised brain vasculature, excessive microgliosis, cellular aging such as break down of the nuclear membrane and consequently escape of TDP-43 from the nucleus and possible contributions of synuclein. We will explore interactions of these factors with aging through descriptive neuropathology and experimental neuropathology methods. Comparisons will utilize sporadic AD post-mortem from several brain banks. These studies include state of the art single cell RNAseq and advanced assessment of inflammation markers. Cellular models will be explored using human induced pluripotent stem cell-derived neurons that harbor the PSEN1[E280A] mutation and are intended to discover downstream pathways affected by the mutation. Co-cultures with microglia to capture autonomous and non-autonomous effects of the mutation will be determined. To accomplish the aims we have assembled a multi-institutional international team with a long history of collaboration. Dr. Lopera, who first recognized the families and manages the Alzheimer Prevention Trial, heads the team in Colombia, an NIH supported project. To support the neuropathology effort we have enlisted the expertise of Dr. Eric Huang. Kosik has a nearly 30 year collaboration with Lopera, is familiar with the conduct of research in Colombia and recently traveled to visit the Colombian brain bank with Eric Huang. Kosik is closely connected institutionally with UCSF through his role as co-director of the Tau Consortium along with Bruce Miller. Kosik has published with Ellisman and serves on the review board for the National Center for Microscopy and Imaging Research center at UCSD. Thus the project consists of a strong, experienced and highly integrated team capable of conducting a complex project and dealing with any of the obstacles that will inevitably arise.